Ferro-alloys, widely used in making alloy steels, are compositions consisting mainly of iron and noneferrous metal with the latter predominating. Aside from carbon, the compositions may also include such nonmetallic constituents as silicon, sulfur and phosphorus as well as various impurities.
The removal of carbon by oxidation is well known in the refining of pig iron. It has also been proposed to adapt this technique to the refining of a mixture of pig iron and ferrochrome for the production of low-carbon chromium-alloy steel; see U.S. Pat. No. 3,751,242. As described in that patent, a prerefined pig-rion melt is admixed with a minor proportion of ferrochrome in a converter whereupon a jet of oxygen is introduced through a nozzle within a sheath of protective gas.
A problem generally encountered in the refining of ferrochrome and ferromanganese, even when use is made of a protective jacket gas, is the formation of high-melting chromium and manganese oxides from which these nonferrous metals can be recovered only by relatively expensive chemical reduction. This is particularly true where the nonferrous metal, i.e. the chromium or the manganese, is present in a proportion of more than 50% by weight so as to form the predominant constituent of the ferro-alloy.